Camshaft adjusters are used in internal combustion engine for varying the control times of the combustion chamber valves, in order to be able to vary the phase relation between the crankshaft and camshaft in a defined angular range between a maximum advanced position and a maximum retarded position. Adapting the control times to the current load and rotational speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated in a drive train by which a torque is transferred from the crankshaft to the camshaft. This drive train can be realized, for example, as a belt, chain, or gearwheel drive.
In a hydraulic camshaft adjuster, the driven element and the drive element form one or more pairs of pressure chambers that act against each other and can be pressurized with oil pressure. The drive element and driven element are here arranged coaxial to each other. By filling and emptying individual pressure chambers, a relative movement between the drive element and driven element is generated. The spring causing rotation between the drive element and the driven element forces the drive element in a preferred direction against the driven element. This preferred direction can be in the same direction or opposite the direction of rotation.
One common construction of a hydraulic camshaft adjuster is the vane cell adjuster. Vane cell adjusters have a stator, a rotor, and a drive element. The rotor is usually locked in rotation with the camshaft and forms the driven element. The stator and the drive element are likewise locked in rotation with each other and are optionally also constructed in one piece. Here, the rotor is located coaxial to the stator and within the stator. With their vanes extending in the radial direction, the rotor and stator form oil chambers that act in opposite directions and can be pressurized by oil pressure and allow a relative movement between the stator and rotor. Furthermore, the vane cell adjusters have various sealing covers. The stator, drive element, and sealing covers are secured by several screw connections.
Another known construction of hydraulic camshaft adjusters is the axial piston adjuster. Here, a displacement element is displaced in the axial direction by oil pressure, wherein this displacement element generates a relative rotation between a drive element and a driven element via helical gearing.
Another construction of a camshaft is the electromechanical camshaft adjuster that has a triple-shaft gearing (for example, a planetary gear). Here, one of the shafts forms the drive element and a second shaft forms the driven element. Through the use of the third shaft, rotational energy can be fed to the system by an adjustment device, for example, an electric motor or a brake, or can be discharged from the system. Here, a spring can likewise be arranged such that the drive element and the driven element are supported or restored in a relative rotation.
DE 10 2006 002 993 A1 discloses a camshaft adjuster in which the spring element is arranged on the side of the camshaft adjuster facing the camshaft. The spring element is covered by a spring cover. The cover secures the spring element in the axial direction and protects against external effects.
DE 10 2008 051 755 A1 discloses a camshaft adjuster with a spring element, wherein one end of the spring element is supported on a pin that is screwed with a washer. A pot-shaped spring cover encapsulates the spring element with this washer and protects against external effects.